<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <link rel="stylesheet" href="./style.css">
  <style>
    .item{
      float: left;
      height: 400px;
      width: 100%;
    }
    .item:nth-last-child(2),
    .item:nth-last-child(2) ~ .item{
      width: 50%;
    }
    .item:nth-last-child(3),
    .item:nth-last-child(3) ~ .item{
      width: 33.3%;
    }
  </style>
</head>
<body>
  <div class="wrap">
    <div class="item">1</div>
    <div class="item">2</div>
    <div class="item">
      <form method="POST" action="/search">
        <input type="text">
      </form>
    </div>
  </div>
</body>
</html>